Various chemical oxygen acceptors are known in the prior art.
In U.S. Pat. No. 2,418,402 a process for the recovery of oxygen utilizes a combination of metallic chlorides as an oxygen absorbing material.
A strontium oxide-peroxide reaction mass is used in U.S. Pat. No. 3,579,292 in order to provide an oxygen absorbing medium for the recovery of oxygen from a gas stream.
In U.S. Pat. No. 3,856,928 a combination of magnesium oxide, calcium oxide and barium oxide are utilized to recover oxygen from an air stream. A lean air stream from the process is combusted with fuel, heat exchanged, combusted with additional fuel or combined with steam before being expanded in a turbine for the recovery of power, after which the expanded lean air product is heat exchanged against feed air to the process.
U.S. Pat. No. 3,980,763 discloses the use of praseodymium and cerium oxides as oxygen carriers in a cyclic oxidation-reduction process for the separation of oxygen from air.
The use of zeolitic molecular sieve beds in a pressure swing adsorption process is disclosed in U.S. Pat. No. 4,026,680. That patent does not constitute a chemical acting adsorption scheme.
U.S. Pat. No. 4,089,938 teaches the use of a suspension of manganese dioxide in an aqueous solution of sodium or potassium hydroxide as an oxygen absorbing medium for the recovery of oxygen from air. The vented oxygen-depleted gas stream is heat exchanged with the feed gas stream to the absorption zone of the process.
U.S. Pat. No. 4,287,170, to the present inventor, discloses a chemical absorption process for the recovery of both oxygen product and nitrogen product, wherein the nitrogen product is further separated from oxygen in a scavenging cycle before expansion in a turbine. The nitrogen product is heat exchanged against the incoming feed air stream to the overall process.
The use of alkali metal salts comprising molten solutions of nitrate and nitrite, wherein the ratio of nitrate to nitrite is maintained greater than 0.3 for the separation of oxygen from air is set forth in U.S. Pat. No. 4,132,766, also to the present inventor. The oxygen-depleted air stream is expanded through a turbine in order to provide power for the compression of the feed air stream. The oxygen-depleted air stream is also contemplated for partial expansion, reheating and then additional expansion. The stream is then contemplated for optional combustion in order to provide heat for the heater 8 of the process flow scheme.
U.S. Pat. No. 4,340,578 to the present inventor, discloses specific compositions of alkali metal nitrates and nitrites, which can be used in an oxygen producing chemical absorption process. The process contemplates the combustion of the oxygen-depleted air stream with fuel in a combustion zone 6 prior to expansion in a turbine 7 and heat exchange of the expanded stream with the feed air stream in a heat exchanger 4 for further expansion in the turbine 8.
Despite the various disclosures of chemical oxygen absorber processes, the prior art has failed to provide an overall integrated process, which is energy efficient and provides conservation of process materials, along with compatability of process streams with process equipment. The present invention is deemed to provide such advantages.